<template>
  <div class="pagination">
    <button :disabled="pageNo===1" @click="getPageNo(pageNo-1)">上一页</button>
    <button v-if="numberStarAndEnd.start > 1" @click="getPageNo(1)" :class="{active:pageNo===1}">1</button>
    <button v-if="numberStarAndEnd.start > 2">···</button>

    <button v-for="(number,index) in iteratorArray" :key="index" @click="getPageNo(number)"
            :class="{active:pageNo===number}">{{ number }}
    </button>

    <button v-if="totalPage - numberStarAndEnd.end >= 2">···</button>
    <button v-if="totalPage - numberStarAndEnd.end >= 1" @click="getPageNo(totalPage)"
            :class="{active:pageNo===totalPage}">{{ totalPage }}
    </button>
    <button :disabled="pageNo===totalPage" @click="getPageNo(pageNo+1)">下一页</button>

    <button style="margin-left: 30px">共 {{ total }} 条</button>
  </div>
</template>

<script>
export default {
  // eslint-disable-next-line vue/multi-word-component-names
  name: "Pagination",
  props: ['pageNo', 'pageSize', 'total', 'continues'],
  computed: {
    totalPage() {
      //总页数
      return Math.ceil(this.total / this.pageSize)//向上取整数
    },
    gapPage() {
      return parseInt((this.continues / 2).toString())
    },
    numberStarAndEnd() {
      let start = 0
      let end = 0
      if (this.continues > this.totalPage) {
        //连续的页码比总页码还大，需要考虑这种异常状态
        start = 1
        end = this.totalPage
      } else {
        start = this.pageNo - this.gapPage
        end = this.pageNo + this.gapPage
        //处理start等于非正整数时的情况
        if (start < 1) {
          start = 1
          end = this.continues
        }
        if (end > this.totalPage) {
          start = this.totalPage - this.continues + 1
          end = this.totalPage
        }
      }
      return {start, end}
    },
    iteratorArray() {
      let arr = []
      for (let i = this.numberStarAndEnd.start; i < this.numberStarAndEnd.end + 1; i++) {
        arr.push(i);
      }
      return arr
    },
  },
  methods: {
    getPageNo(pageNo) {
      this.$emit('getPageNo', pageNo)
    }
  }
}
</script>

<style lang="less" scoped>
.pagination {
  text-align: center;

  button {
    margin: 0 5px;
    background-color: #f4f4f5;
    color: #606266;
    outline: none;
    border-radius: 2px;
    padding: 0 4px;
    vertical-align: top;
    display: inline-block;
    font-size: 13px;
    min-width: 35.5px;
    height: 28px;
    line-height: 28px;
    cursor: pointer;
    box-sizing: border-box;
    text-align: center;
    border: 0;

    &[disabled] {
      color: #c0c4cc;
      cursor: not-allowed;
    }

    &.active {
      cursor: not-allowed;
      background-color: #409eff;
      color: #fff;
    }
  }
}

.active {
  background-color: skyblue;
}
</style>